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35 /*! \libinternal
36 * \file
37 * \brief Declares special case of 3x3 matrix frequently used, and associated functions.
38 *
39 * \author Christian Blau <cblau@gwdg.de>
40 * \ingroup module_math
41 */
42
43 #ifndef GMX_MATH_MATRIX_H_
44 #define GMX_MATH_MATRIX_H_
45
46 #include <array>
47
48 #include "gromacs/math/multidimarray.h"
49 #include "gromacs/math/utilities.h"
50 #include "gromacs/math/vec.h"
51 #include "gromacs/utility/real.h"
52
53 namespace gmx
54 {
55
56 /*! \brief Three-by-three matrix of ElementType.
57 * \tparam ElementType type of element to be stored in matrix
58 */
59 template<class ElementType>
60 using BasicMatrix3x3 = MultiDimArray<std::array<ElementType, 3 * 3>, extents<3, 3>>;
61
62 /*! \brief Three-by-three real number matrix.
63 * \note will replace the C-style real[3][3] "matrix"
64 */
65 using Matrix3x3 = BasicMatrix3x3<real>;
66 //! Convenience alias for a matrix view
67 using Matrix3x3Span = Matrix3x3::view_type;
68 //! Convenience alias for a const matrix view
69 using Matrix3x3ConstSpan = Matrix3x3::const_view_type;
70
71 //! Determinant of a 3x3 matrix
determinant(Matrix3x3ConstSpan matrix)72 constexpr real determinant(Matrix3x3ConstSpan matrix)
73 {
74 return (matrix(0, 0) * (matrix(1, 1) * matrix(2, 2) - matrix(2, 1) * matrix(1, 2))
75 - matrix(1, 0) * (matrix(0, 1) * matrix(2, 2) - matrix(2, 1) * matrix(0, 2))
76 + matrix(2, 0) * (matrix(0, 1) * matrix(1, 2) - matrix(1, 1) * matrix(0, 2)));
77 }
78
79 //! Calculates the trace of a 3x3 matrix view
trace(Matrix3x3ConstSpan matrixView)80 constexpr real trace(Matrix3x3ConstSpan matrixView)
81 {
82 return matrixView(0, 0) + matrixView(1, 1) + matrixView(2, 2);
83 }
84
85 /*! \brief Create an identity matrix of ElementType with N * M elements.
86 *
87 * \tparam ElementType type of matrix elements
88 * \tparam N number of rows
89 * \tparam M number of columns, defaults to number of rows if not set
90 *
91 * \returns a matrix with values one where row equals column index and null
92 * where row does not equal column index
93 */
94 template<typename ElementType, int N, int M = N>
identityMatrix()95 MultiDimArray<std::array<ElementType, N * M>, extents<N, M>> identityMatrix()
96 {
97 std::array<ElementType, N * M> matrixEntries{};
98 MultiDimArray<std::array<ElementType, N * M>, extents<N, M>> idMatrix(matrixEntries);
99 for (int i = 0; i < std::min(N, M); i++)
100 {
101 idMatrix(i, i) = 1;
102 }
103 return idMatrix;
104 }
105
106 //! Calculate the transpose of a 3x3 matrix, from its view
107 Matrix3x3 transpose(Matrix3x3ConstSpan matrixView);
108
109 //! Multiply matrix with vector.
110 void matrixVectorMultiply(Matrix3x3ConstSpan matrix, RVec* v);
111
112 //! Create new matrix type from legacy type.
createMatrix3x3FromLegacyMatrix(const matrix legacyMatrix)113 static inline Matrix3x3 createMatrix3x3FromLegacyMatrix(const matrix legacyMatrix)
114 {
115 GMX_RELEASE_ASSERT(legacyMatrix, "Need valid legacy matrix");
116 Matrix3x3 newMatrix;
117 for (int i = 0; i < DIM; i++)
118 {
119 for (int j = 0; j < DIM; j++)
120 {
121 newMatrix(i, j) = legacyMatrix[i][j];
122 }
123 }
124 return newMatrix;
125 }
126
127 //! Fill legacy matrix from new matrix type.
fillLegacyMatrix(Matrix3x3ConstSpan newMatrix,matrix legacyMatrix)128 static inline void fillLegacyMatrix(Matrix3x3ConstSpan newMatrix, matrix legacyMatrix)
129 {
130 GMX_RELEASE_ASSERT(legacyMatrix, "Need valid legacy matrix");
131 for (int i = 0; i < DIM; i++)
132 {
133 for (int j = 0; j < DIM; j++)
134 {
135 legacyMatrix[i][j] = newMatrix(i, j);
136 }
137 }
138 }
139
140 } // namespace gmx
141
142 #endif
143